1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a backlight module and a liquid crystal display device using the backlight module.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal panel and a backlight module. The operation principle of the liquid crystal panel is that liquid crystal molecules are interposed between two parallel glass substrates and the liquid crystal molecules are controlled to change direction by application of electricity to the glass substrates in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of an LCD. The backlight module can be classified in two types, namely side-edge backlight module and direct backlight module, according to the position where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the back side of the liquid crystal panel to form a planar light source that directly provides lighting to the liquid crystal panel. The side-edge backlight module comprises a backlight source, such as an LED light bar, arranged at an edge of a backplane to be located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters an optic film assembly through a light incident face of the optic film assembly and is projected out of a light emergence face of the optic film assembly, after being reflected and diffused, to thereby form a planar light source for the liquid crystal panel.
In the conventional light source, LED or CCFL emits white light by mixing lights emitting from fluorescent powders, which renders color gamut narrow and color reproducibility poor, making it not able to restore the true color of an object. Thus, a new backlighting mode is proposed, which uses sun light that has the most complete color gamut and the strongest color reproducibility to serve as backlight source. Optic fibers are employed to conduct sun light to the backlight system to provide backlighting to a liquid crystal panel, making the screen of the liquid crystal panel more vivid and having stronger color integrity. In addition, sun light also meets the current trend of environmental protection.
As shown in FIGS. 1 and 2, which are schematic views showing a backlight module and a liquid crystal display device using sun light as backlight source, the liquid crystal display device comprises a back panel 100, a light guide plate 300 arranged in the back panel 100, an optic fiber substrate 500 arranged at the side of light incidence surface of the light guide plate 300, a plurality of optic fibers 700 connected to the optic fiber substrate 500, an intermediate frame 800 mounted on the back panel 100, and a liquid crystal display panel 900 positioned on the intermediate frame 800. The optic fibers 700 each have an end connected to the optic fiber substrate 500 and an opposite end connected to sun light collector (not shown). The sun light collector collects sun light and transmits the sun light through the optic fibers 700 to the optic fiber substrate 500 to allow the sun light to enter the light guide plate 300 from the light incidence surface of the light guide plate 300 and emerges from a light emergence surface of the light guide plate 300 to provide a uniformly distributed planar light source to the liquid crystal display panel 900. After entering the light guide plate 300, the light must travel a distance for light mixing. However, when a small number of optic fibers 700 are used, the light mixing distance must be extended, otherwise the so-called firebug effect may occur at the light incidence side, showing a plurality of light spots. However, increasing the light mixing distance needs to increase the thickness of the bezel and this affects the outside appearance of the liquid crystal display device. Using a large number of optic fibers 700 would overcome the problem of firebug effect, but the increased number of optic fibers 700 between the light collector and the light incidence site would increase the cost, making it disadvantageous for cost control.